Coan P M, Ferguson-Smith A C, Burton G J
Department of Anatomy, University of Cambridge, UK.
J Anat. 2005 Dec;207(6):783-96. doi: 10.1111/j.1469-7580.2005.00488.x.
The mouse is an extremely useful experimental model for the study of human disease owing to the ease of genetic and physiological manipulation. A more detailed knowledge of murine placental development will, we hope, increase our understanding of the pathogenesis of placentally related complications of human pregnancy. The murine placenta consists of two main fetally derived compartments: the labyrinthine zone and the junctional zone. Exchange in the labyrinthine zone takes place across an interhaemal membrane comprising an outer layer of cytotrophoblast cells and two inner layers of syncytial trophoblast. The cytotrophoblast layer thins as gestation advances, and in addition becomes highly perforated after embryonic day (E)12.5. Furthermore, as gestation advances cytotrophoblast nuclear volume and DNA content increase, suggesting the formation of labyrinthine trophoblast giant cells. The syncytial layers become increasingly microvillous, enlarging the surface area for exchange. Separate basement membranes support the syncytium and the fetal capillary endothelium throughout gestation, although these appear to fuse where the capillaries are closely approximated to the trophoblast. The junctional zone consists of two principal trophoblast cell types, spongiotrophoblasts and invasive glycogen cells, yet the functions of each remain elusive. Spongiotrophoblasts vary in their appearance even when not fully differentiated, but a striking feature is the extensive endoplasmic reticulum of the more mature cells. Early glycogen cells are distinguished by the presence of electron-dense glycogen granules, and large amounts of surrounding extracellular matrix. Later the accumulations of glycogen granules occupy almost all the cytoplasm and there are few organelles. This is the first study to use both scanning and transmission electron microscopy in an ultrastructural description of murine placental development and is complementary to contemporary genetic investigations.
由于易于进行基因和生理操作，小鼠是研究人类疾病的极其有用的实验模型。我们希望，对小鼠胎盘发育的更详细了解将增进我们对人类妊娠中与胎盘相关并发症发病机制的认识。小鼠胎盘由两个主要的胎儿来源部分组成：迷路区和连接区。迷路区的物质交换通过血-血膜进行，该血-血膜由一层外层细胞滋养层细胞和两层内层合体滋养层组成。随着妊娠进展，细胞滋养层变薄，并且在胚胎第12.5天（E12.5）后还会变得高度穿孔。此外，随着妊娠进展，细胞滋养层细胞核体积和DNA含量增加，提示迷路滋养层巨细胞的形成。合体层的微绒毛越来越多，扩大了交换表面积。在整个妊娠期间，单独的基底膜支撑着合体层和胎儿毛细血管内皮，尽管在毛细血管与滋养层紧密相邻的地方它们似乎会融合。连接区由两种主要的滋养层细胞类型组成，即海绵滋养层细胞和侵入性糖原细胞，但其各自的功能仍不清楚。即使未完全分化，海绵滋养层细胞的外观也有所不同，但一个显著特征是较成熟细胞的内质网广泛。早期糖原细胞的特征是存在电子致密的糖原颗粒以及大量周围的细胞外基质。后来，糖原颗粒的积累几乎占据了所有细胞质，细胞器很少。这是第一项同时使用扫描电子显微镜和透射电子显微镜对小鼠胎盘发育进行超微结构描述的研究，并且是对当代基因研究的补充。
